Method for producing metallic-sodium-filled engine valve

ABSTRACT

In the disclosed method, an engine valve (V) filled with metallic sodium (Na) within is produced by means of hardening metallic sodium (Na)—that has been liquefied through heat-melting—into rods by linearly discharging the metallic sodium (Na) in a liquid hydrocarbon ( 120 ), thus cooling the metallic sodium, then inserting these rods into a hollow section (H) through the opening (M) of a stem section (S) , and then sealing the opening (M).

TECHNICAL FIELD

The present invention relates to a method for producing an engine valvefilled inside with metallic sodium.

BACKGROUND ART

In an engine valve of an automobile or the like, in order to respond toan increase in performance, a reduction in fuel consumption of anengine, and the like, the weight is reduced and the heat transmission isincreased by filling an inside of the engine valve with metallic sodium.

Such an engine valve has a stem portion which has a hollow portionformed in an inner portion and which has an opening formed at an upperend. To this stem portion, for example, (1) solid metallic sodium isextruded into a bar shape, cut into a predetermined length, and theninserted into the hollow portion from the opening; or (2) solid metallicsodium is heated to melt (about 120° C. to 300° C.) into a liquid stateand then put into the hollow portion by injecting a predetermined amountof metallic sodium into the hollow portion from the opening. Thereafter,the opening is sealed and the engine valve is thus produced (forexample, see Patent Literatures 1 to 3 and the like listed below).

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Patent Application Publication No. Hei03-018605

Patent Literature 2: Japanese Patent Application Publication No. Hei04-232318

Patent Literature 3: Japanese Patent Application Publication No. Hei04-272413

SUMMARY OF INVENTION Technical Problem

However, a conventional method for producing a metallic-sodium-filledengine valve as described above has the following problems.

(1) Solid metallic sodium is difficult to extrude and the workability ofshaping the solid metallic sodium is thereby poor.(2) When liquid metallic sodium adheres to an inner wall of theelongated hollow portion (a diameter of about 2 to 4 mm) during theinjection of liquid metallic sodium into the hollow portion, metallicsodium immediately cools and becomes solid thereby closing the hollowportion. Thus, the liquid metallic sodium needs to be injected while thestem portion is heated (98° C. or higher) and the workability ofinjection is thereby poor.

The present invention is made in view of the problems describe above,and an object thereof is to provide a method for producing ametallic-sodium-filled engine valve by which metallic sodium can beeasily put into the inside of an engine valve.

Solution to Problem

In a method for producing an engine valve filled inside with metallicsodium, according to a first aspect of the invention for solving theaforementioned problems, the engine valve is produced by: puttingmetallic sodium into a hollow portion from an opening of a stem portionhaving the hollow portion in an inner portion and having the opening atan upper end; and thereafter sealing the opening, the methodcharacterized by comprising: cooling and solidifying metallic sodiumheated and melted to a liquid state into a bar-shaped piece; andthereafter inserting the bar-shaped piece of metallic sodium into thehollow portion from the opening of the stem portion.

The method for producing a metallic-sodium-filled engine valve accordingto a second aspect of the invention is characterized in that, in thefirst aspect of the invention, the metallic sodium heated and melted toa liquid state is discharged linearly into a hydrocarbon-based liquidand is cooled to be solidified into the bar-shaped piece.

The method for producing a metallic-sodium-filled engine valve accordingto a third aspect of the invention is characterized in that, in thefirst aspect of the invention, the metallic sodium heated and melted toa liquid state is injected into a bar-shaped space in an inside of ametal mold having the space in the inside and is then cooled to besolidified into the bar-shaped piece.

The method for producing a metallic-sodium-filled engine valve accordingto a fourth aspect of the invention is characterized in that, in thethird aspect of the invention, the bar-shaped space of the metal mold isformed such that at least an end portion on one side is formed in atapered shape or an elongated ellipse shape.

Advantageous Effects of Invention

In the method for producing a metallic-sodium-filled engine valve of thepresent invention, the metallic sodium heated and melted to a liquidstate is cooled to be solidified into a bar-shaped piece and thebar-shaped piece of metallic sodium is thereafter inserted into thehollow portion from the opening of the stem portion. Thus, thebar-shaped piece of metallic sodium can be easily shaped withoutperforming extrusion and a predetermined amount of metallic sodium canbe easily put into the hollow portion without heating the stem portionof the engine valve.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a view for explaining a first embodiment of a methodfor producing a metallic-sodium-filled engine valve of the presentinvention.

[FIG. 2] FIG. 2 is an explanatory view subsequent to FIG. 1.

[FIG. 3] FIG. 3 is a view for explaining a second embodiment of a methodfor producing a metallic-sodium-filled engine valve of the presentinvention.

[FIG. 4] FIG. 4 is an explanatory view subsequent to FIG. 3.

DESCRIPTION OF EMBODIMENTS

Embodiments of a method for producing a metallic-sodium-filled enginevalve of the present invention are described below based on thedrawings. However, the present invention is not limited to theembodiments described below based on the drawings.

First Embodiment

A first embodiment of a method for producing a metallic-sodium-filledengine valve of the present invention is described based on FIGS. 1, 2.

In FIG. 1, a cylinder is denoted by reference numeral 111 and isprovided with a nozzle 112 on a leading end side. A piston is denoted byreference numeral 113 and is disposed in the cylinder 111 to beslidingly moveable. A piston rod is denoted by reference numeral 114 andis connected to the piston 113 to cause the piston 113 to move. A heateris denoted by reference numeral 115 and is disposed to cover an outerperiphery of the cylinder 111 and also configured to be capable ofheating the inside of the cylinder 111 and keeping it warm (for example,about 120° C. to 300° C.) Reference numeral 121 denotes a container anda hydrocarbon-based liquid 120 such as an oil is put in the container121.

In a dry inert gas atmosphere such as a dry nitride gas: the cylinder111 is arranged above the container 121 with the nozzle 112 facingdownward; a piece of solid metallic sodium Na cut out in a predeterminedsize is put into an inside of the cylinder 111 and the piston 113 isinserted into the inside of the cylinder 111; the heater 115 isactivated to heat and melt the piece of metallic sodium Na to a liquidstate; the piston 113 is then pushed by using the piston rod 114 and themetallic sodium Na melted to a liquid state is thereby dischargedlinearly (in a bar shape) from the nozzle 112; and the discharged pieceof metallic sodium Na falls into the hydrocarbon-based liquid 120 in thecontainer 121 and is cooled to a room temperature to be solidified whilemaintaining its linear shape (bar shape).

Next, as shown in FIG. 2, the bar-shaped piece of metallic sodium Na ofa predetermined amount is inserted from an opening M at an upper end ofa stem portion S in such a way that the bar-shaped piece of metallicsodium Na is put into a hollow portion H in an inner portion of the stemportion S. Thereafter, the opening M is closed. Thus, an engine valve Vfilled inside with the predetermined amount of metallic sodium Na can beobtained.

In other words, in the embodiment, metallic sodium Na heated and meltedto a liquid state is discharged linearly (in a bar shape) into thehydrocarbon-based liquid 120, cooled to the room temperature to besolidified, and is then inserted into the hollow portion H from theopening M of the stem portion S.

Thus, in the embodiment, the bar-shaped piece of metallic sodium Na canbe easily shaped without performing extrusion and the predeterminedamount of metallic sodium Na can be easily put into the hollow portion Hwithout heating (98° C. or higher) the stem portion S of the enginevalve V.

Accordingly, in the embodiment, the predetermined amount of metallicsodium Na can be easily put into the inside of the engine valve V.

Moreover, Patent Literature 2 and the like have the following problem.In Patent Literature 2, metallic sodium Na is cooled and solidified bycausing coolant such as liquid nitrogen to flow out from a nozzle whenthe metallic sodium Na heated and melted is sent out from the nozzle.Thus, moisture in the air is also cooled and frost is formed on asurface of cooled metallic sodium Na. As a result, the moisture and themetallic sodium Na react with each other. However, in the embodiment,the metallic sodium Na heated and melted is cooled and solidified bycausing the metallic sodium Na to fall into the hydrocarbon-based liquid120. Thus, the formation of frost on the surface of cooled metallicsodium Na can be surely prevented.

Second Embodiment

A second embodiment of a method for producing a metallic-sodium-filledengine valve of the present invention is described based on FIGS. 3, 4.Note that, portions same as the first embodiment are denoted with thesame reference numerals as those used in the descriptions of theaforementioned first embodiment and descriptions which overlap with thedescriptions of the aforementioned first embodiment are omitted.

In FIG. 3, a metal mold is denoted by reference numeral 220 and isconfigured such that a bar-shaped space 220 a whose end portionsrespectively on both sides are tapered is formed by causing a top faceof a lower mold 221 and a bottom face of an upper mold 222 to overlapeach other. In a top face of the upper mold 222, a communication port222 a communicating the space 220 a and a space above the top facethereof is formed.

In a dry inert gas atmosphere such as a dry nitride gas: the nozzle 112is inserted into the communication port 222 a in the upper mold 222 ofthe metal mold 220; a piece of solid metallic sodium Na cut out in apredetermined size is put into an inside of the cylinder 111 and thepiston 113 is inserted into the inside of the cylinder 111; the heater115 is activated to heat and melt the piece of metallic sodium Na to aliquid state; and the piston 113 is then pushed by using the piston rod114 and the metallic sodium Na melted to a liquid state is therebyinjected into the space 220 a from the communication port 222 a of themetal mold 220 through the nozzle 112.

After a predetermined amount of metallic sodium Na is injected into thespace 220 a of the metal mold 220, the nozzle 112 is removed from thecommunication port 222 a of the metal mold 220 and the metal mold 220 isthen left to cool to a room temperature. When the metal mold 220 cools,the metallic sodium Na in the space 220 a of the metal mold 220 issolidified into a piece having a shape of the space 220 a, i.e. the barshape whose end portions respectively on both sides are tapered.

Next, the lower mold 221 and the upper mold 222 of the metal mold 220are separated from each other and the piece of metallic sodium Nasolidified in the bar shape having the tapered end portions is takenout. Then, as shown in FIG. 4, the piece of metallic sodium Na isinserted from the opening M at the upper end of the stem portion S insuch a way that the piece of metallic sodium Na is put into the hollowportion H in the inner portion of the stem portion S. Thereafter, theopening M is closed. Thus, the engine valve V filled inside with thepredetermined amount of metallic sodium Na can be obtained.

In the first embodiment, the bar-shaped piece of metallic sodium Na isshaped as follows. The metallic sodium Na heated and melted to a liquidstate is discharged linearly (in a bar shape) into the hydrocarbon-basedliquid 120 and then cooled to the room temperature to be solidified.However, in the second embodiment, the bar-shaped piece of metallicsodium Na having the tapered end portions is shaped as follows. Themetallic sodium Na heated and melted to a liquid state is injected intothe space 220 a in the metal mold 220 from the communication port 222 aof the metal mold 220 and then cooled to the room temperature to besolidified.

Thus, in the second embodiment, the bar-shaped piece of metallic sodiumNa can be easily shaped without performing extrusion and metallic sodiumNa can be put into the hollow portion H without heating (98° C. orhigher) the stem portion S of the engine valve V, as similar to thefirst embodiment.

Accordingly, in the second embodiment, the predetermined amount ofmetallic sodium Na can be easily put into the inside of the engine valveV as in the first embodiment as a matter of course. Furthermore, it ispossible to easily obtain the bar-shaped piece of metallic sodium Nashaped such that end portions thereof respectively on both sides aretapered, i.e. the bar-shaped piece of metallic sodium Na which can beeasily inserted into the elongated hollow portion H (a diameter of about2 to 4 mm). In addition, the piece of metallic sodium Na can be insertedinto the inside of the engine valve V more easily.

Other Embodiments

In the aforementioned first embodiment, the piece of metallic sodium Namay be obtained as follows. The metallic sodium Na discharged linearly(in a bar shape) is caused to continuously fall into thehydrocarbon-based liquid 120 and then cooled to be solidified in such away that an elongated bar material of metallic sodium Na is obtained.Thereafter, the bar material is cut in a required length and the cutpiece is put into the hollow portion H of the engine valve V.Alternatively, the piece of metallic sodium Na may be obtained asfollows. The metallic sodium Na is caused to intermittently fall intothe hydrocarbon-based liquid 120 and then cooled to be solidified insuch a way that bar materials of the required length are obtained.Thereafter, each of the bar materials can be inserted into the hollowportion H of the engine valve V without being cut.

In the aforementioned second embodiment, descriptions are given of thecase where the bar shaped piece of metallic sodium Na whose end portionsrespectively on both sides are tapered is shaped with the metal mold220. However, as other embodiments, a bar-shaped piece of metallicsodium Na whose end portion on one side alone is tapered or a bar-shapedpiece of metallic sodium Na having an elongated ellipse shape may beshaped with a metal mold, for example. Even in such cases, operationaleffects similar to the case of the aforementioned second embodiment canbe obtained.

Moreover, in the aforementioned second embodiment, descriptions aregiven of the case where the bar-shaped piece of metallic sodium Na isobtained one by one by using the metal mold 220 having the single space220 a. However, as another embodiment, it is also possible to obtainmultiple bar-shaped pieces of metallic sodium Na simultaneously byusing, for example, a metal mold having multiple spaces.

INDUSTRIAL APPLICABILITY

In the method for producing a metallic-sodium-filled engine valve of thepresent invention, the bar-shaped piece of metallic sodium can be easilyshaped without performing extrusion and the predetermined amount ofmetallic sodium can be easily put into the hollow portion withoutheating the stem portion of the engine valve. Thus, the method can beused very effectively in the industrial field.

REFERENCE SIGNS LIST

-   111 cylinder-   111 a discharge port-   112 piston-   113 piston rod-   114 heater-   120 hydrocarbon-based liquid-   121 container-   220 metal mold-   220 a space-   221 lower mold-   222 upper mold-   222 a communication port-   Na metallic sodium-   V engine valve-   A umbrella portion-   S stem portion-   H hollow portion-   M opening

1-4. (canceled)
 5. A method for producing an engine valve filled insidewith metallic sodium, the engine valve produced by: putting metallicsodium into a hollow portion from an opening of a stem portion havingthe hollow portion in an inner portion and having the opening at anupper end; and thereafter sealing the opening, the method comprising:cooling and solidifying metallic sodium heated and melted to a liquidstate into a bar-shaped piece; and thereafter inserting the bar-shapedpiece of metallic sodium into the hollow portion from the opening of thestem portion.
 6. The method for producing a metallic-sodium-filledengine valve according to claim 5, wherein the metallic sodium heatedand melted to a liquid state is discharged linearly into ahydrocarbon-based liquid and is cooled to be solidified into thebar-shaped piece.
 7. The method for producing a metallic-sodium-filledengine valve according to claim 5, wherein the metallic sodium heatedand melted to a liquid state is injected into a bar-shaped space in aninside of a metal mold having the space in the inside and is then cooledto be solidified into the bar-shaped piece.
 8. The method for producinga metallic-sodium-filled engine valve according to claim 7, wherein thebar-shaped space of the metal mold is formed such that at least an endportion on one side is formed in a tapered shape or an elongated ellipseshape.